Surfaces Ostwald ripening

There aie a number of major indusuial problems in the operation of the steam reforming of metlrane. These include the formation of carbon on the surface of the catalyst, the sulphidation of the catalyst by the H2S impurity in commercial natural gas, and die decline of catalytic activity due to Ostwald ripening of the supported catalyst particles by migration of catalyst atoms from the smaller to tire larger particles, as the temperamre is increased. A consideration of tire thermodynamics of the principal reaction alone would suggest that the reaction shifts more favourably to the completion of the reaction as the temperature is increased. 

TBP and injected into a hot ( 350 °C) solution of TOPO (12 g). The injection of CdSe precursors into the hot solution ofTOPO resulted in spontaneous nucleation of CdSe nanocrystals and a decrease in temperature. Once the temperature was stabilized, an additional amount (0.4 mL) of the precursor solution was added for the growth of the nucleated nanocrystals. Here, Ostwald ripening was avoided by separating the nucleation and growth processes. All the reagents and the reaction were kept under an Ar atmosphere to avoid fire hazard and surface oxidation of the nanocrystals. 

Ostwald ripening is driven by the positive surface energy, the specific, per gram amount of which can be lessened with particle growth. The change in Gibbs free energy when a particle forms is composed of two terms, a bulk term and a surface term as... 

Cu0-Ce02-Zr02. 200 Ni-Ce02-ZrC>2, 185 corrosive, 142 Ostwald ripening, 144 surface reconstruction, 142... 

Ostwald ripening consists of a diffusive transfer of the dispersed phase from smaller to larger droplets. Ostwald ripening is characterized by either a constant volume rate [4,5] (diffusion-controlled ripening) or a constant surface rate 22 [6] (surface-controlled ripening), depending on the origin of the transfer mechanism ... 

P. Taylor Ostwald Ripening in Emnlsions. CoUoids Surfaces 99, 175 (1995). 

A.S. Kabalnov, A.V. Pertsov and E.D. Shchukin Ostwald Ripening in Two-Component Disperse Phase Systems Application to Emulsion Stability. Colloid Surfaces 24, 19 (1987). 

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